This invention relates to a sampler for introducing charged particles into a measuring apparatus for measuring charge distribution of the charged particles, and a measuring apparatus provided with such sampler.
There are two widely-used methods, an average charge ratio measuring method and a charge distribution measuring method, as methods for managing property of charged particles such as toner (see KIMURA, Masatoshi: “Toner-Charge Measuring Method (2)-charge amount-”, ELECTROPHOTOGRAPHY, pages 168-174, Vol. 30, No. 2 (1991)). Examples of the average charge ratio measuring method include a Faraday Cage method and a toner blow-off method. These average charge ratio measuring methods have been widely used because of its simplicity.
However, image degradation such as fog and low image density might occur, even if the average charge ratio of toner particles falls within allowable standard range. Thus, such image degradations including fog, need further explanation than the average charge ratio of toner particles.
Accordingly, charge distribution measuring methods are developed to manage such property of charged particles that average charge ratio measuring methods can not explain.
There is an apparatus for measuring charge distribution of toner particles, the apparatus employing one of conventional charge distribution measuring methods. The apparatus introduces the toner particles into an interior chamber thereof, producing a laminar air flow having substantially uniform velocity in the space where toner particles are dispersed. The apparatus measures charge distribution of toner particles by determining how much each of the toner particles is deflected by electric fields generated in the interior chamber (see U.S. Pat. No. 4,375,673).
Another example of the conventional charge distribution measuring methods is Laser Doppler method in which vibration of a sound wave is generated by constant frequency, and electric field is established between parallel plate electrodes, then toner particles are passed through the electric field. In the method, phase lag and deflection factor of the toner particles are measured (see TSUJIMOTO, Hiroyuki, and KAYA, Noriyoshi “Effect of suction air velocity and field voltage on measurement for charge amount by E-SPART analyzer”, the Micromeritics (Funsai in Japanese), Page 48-54, No. 35, (1991)).
Further, another example of the conventional charge distribution measuring methods is a method which eliminates the necessity of controlling the velocity of air flow. In the method, uniform electric field is generated in horizontal direction and charged particles descend in vertical direction by gravitation (see MASUDA, Hiroaki, GOTOH, Kuniaki, and ORITA, Nobuaki: “Charge Distribution Measurement of Aerosol Particles”, the Journal of Aerosol Research, pages 325-332, Vol. 8, No. 4 (1993)).
In addition, there are employed technologies in which charged particles are carried in horizontal direction by traveling-wave electric field, and introduced into an apparatus for measuring charge distribution of the charged particles (see JP2002-311073A and JP2001-116786A).
However, in above mentioned arts, there will be problem that toner particles change in charge amount due to contact with other members during sampling step in which toner particles are separated and introduced into measuring section.
Further, in the measuring apparatus disclosed in U.S. Pat. No. 4,375,673 and TSUJIMOTO et al., there are needed controlling means for controlling velocity of air flow in measuring section in which electric field is established. Such controlling means are generally expensive and cause an inconvenience that charge distribution measuring apparatus become larger.
It is an object of the present invention to provide a sampler that prevents charged particles to be changed in charge amount during sampling step in which the charged particles are introduced by gravity into a measuring apparatus for measuring charge distribution of the charged particles, and a measuring apparatus provided with such sampler.